The present invention relates to a positive photosensitive composition used in a manufacturing process of semiconductors, such as ICs, in a process of producing circuit boards for liquid crystal display and thermal head, and in other photofabrication processes. More specifically, the invention is concerned with a positive photosensitive composition suitable for using far ultraviolet radiation having a wavelength of not longer than 250 nm or the like as an exposure light source.
Chemical amplification positive resist compositions are materials for forming patterns on substrates. Specifically, when those resist compositions are irradiated with far ultraviolet radiation or the like, they generate acids in the irradiated areas, and undergo reaction utilizing the acids as a catalyst to cause a difference in solubility in a developer between the unirradiated areas and irradiated areas with such radiation, thereby enabling the pattern formation.
In the case where KrF excimer laser is used as an exposure light source, a resin containing as its basic skeleton poly(hydroxystyrene) showing weak absorption in the region of 248 nm are used as a main component. Therefore, such a resist composition has high sensitivity and high resolution and can form good-quality patterns compared with traditional resist compositions containing naphthoquinonediazide/navolak resin combination.
However, when a light source of a shorter wavelength, such as ArF exceimer laser (193 nm), is used for exposure, even the aforementioned resist composition of chemical amplification type is not satisfactory, because compound having aromatic group inherently has strong absorption at a wavelength around 193 nm.
Utilization of poly(meth)acrylate as a polymer having weak absorption in the region of 193 nm is described in J. Vac. Sci. Technol., B9, 3357 (1991). However, such a polymer has a problem of being inferior to currently used phenol resins having aromatic groups in resistance to dry etching ordinarily carried out in a manufacturing process of semiconductors.
Japanese Patent Laid-Open No. 2000-292917 discloses the chemical amplification positive resist composition using as an acid generator a mixture of a triarylsulfonium salt type of acid generator and a phenacylsulfonium salt type of acid generator. However, resist compositions currently in use have a problem in that when it is attempted to resolve fine patterns, a pattern collapsing is caused to result in deterioration of resolution. Therefore, solution of such a problem and improvement in line profile are required.
It is therefore an object of the invention to provide a positive photosensitive composition that can form patterns prevented from pattern collapsing even when attempts to resolve fine patterns are made, and achieves improvement in line profile.
Other objects of the invention will become apparent from the following description.
The objects of the invention are attained with positive photosensitive compositions having the following constitutions.
(1) A positive photosensitive composition comprising (A) an acid generator, which generates an acid upon irradiation with actinic ray or radiation, represented by formula (I) shown below, and (B) a resin having a monocyclic or polycyclic alicyclic hydrocarbon structure and being decomposed by the action of an acid to increase dissolution speed in an alkali developer. 
wherein R1 to R5, which may be the same or different, each represent a hydrogen atom, a nitro group, a halogen atom, or an unsubstituted or substituted alkyl, alkoxy, alkyloxycarbonyl, aryl or acylamino group, or at least two of R1 to R5 may combine with each other to form a cyclic structure; R6 and R7, which may be the same or different, each represent a hydrogen atom, a cyano group, or an unsubstituted or substituted alkyl or aryl group; Y1 and Y2, which may be the same or different, each represent an unsubstituted alkyl group, an alkyl group having a substituent, an ether linkage group or a sulfide linkage group, or an unsubstituted or substituted alkenyl group, provided that when both Y1 and Y2 are alkyl groups, at least either Y1 or Y2 has a hydroxy group, an ether linkage group or a sulfide linkage group, or each of the alkyl groups contains at least 2 carbon atoms; at least one of R1 to R5 and at least either Y1 or Y2 may combine with each other to complete a ring, at least one of R1 to R5 and at least either R6 or R7 may combine with each other to complete a ring, at least two structures represented by formula (I) may be linked together in any of the positions of R1 to R7, Y1 and Y2 via a linkage group; and Xxe2x88x92 represents a non-nucleophilic anion.
(2) The positive photosensitive composition as described in (1), which further comprises (C) a basic compound and (D) a fluorine-contained and/or silicon-contained surfactant.
(3) The positive photosensitive composition as described in (2), wherein the basic compound (C) is a compound having at least one structure selected from an imidazole structure, a diazabicyclo structure, an onium hydroxide structure, an onium carboxylate structure, a trialkylamine structure and an aniline structure.
(4) The positive photosensitive composition as described in any one of (1) to (3), which further comprises (F) a dissolution-inhibiting low-molecular compound having a molecular weight of at most 3,000 and a group capable of being decomposed by the action of an acid to increase solubility in an alkali developer.
(5) The positive photosensitive composition as described in any one of (1) to (4), wherein the resin (B) further contains a repeating unit having a lactone structure.
In addition, a preferred embodiment of the invention is described below.
(6) The positive photosensitive composition as described in any one of (1) to (5), which further comprises (E) a mixture of a hydroxyl group-containing solvent and a hydroxyl group-free solvent.